The present invention relates to an information recording/reproducing device such as an optical disk device and a magnetic disk device. Specifically, the present invention relates to a method of controlling positioning of a recording/reproducing head which intends to position the recording/reproducing head on a desired track of a rotary disk-shape recording medium with concentric or spiral tracks, and more particularly to a method of controlling positioning of a recording/reproducing head and an information recording/reproducing device which use a speed detecting method which can precisely detect the relative speed of the recording/reproducing head for a track.
In a magnetic disk device, a previously known seeking system positions a recording/reproducing head on a target track of a disk-shape recording medium by detecting the relative speed of the recording/reproducing head for a track using a sum of a differentiated value of the position information obtained when the head traverses each track and an integrated value of the driving current for shifting the head.
Such a system controls the moving speed of the recording/reproducing head on the basis of a speed signal which is a sum of the differential signal of position information obtained from a track in seeking and the integral signal of an actuator driving current for the head. In this case, the differential signal, although it is the relative speed signal of the head for a track, is an intermittent and relatively high frequency component signal so that it cannot detect a change in the relative speed having a continuous and relatively low frequency component due to eccentricity and cannot transmit the detected change. On the other hand, the integral signal, although it is a continuous and relatively low frequency component signal, is the absolute speed signal of the head but not the relative speed so that it cannot also detect a change in the relative speed due to eccentricity and transmit the detected change. As a result, the known system cannot precisely detect a change in the relative speed which results from track swing due to eccentricity and cannot control the head so that it is swiftly positioned on a target track.